JP2003141722A - Optical disk discriminating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately discriminate a disk with few variation by apparatuses. SOLUTION: The optical disk discriminating device is provided with a brightness detection circuit 6 to measure brightness reflected by the information recording surface of an optical disk, a storage means 9 to store a threshold value of brightness, and a control circuit 8 to discriminate an optical disk 1 having different reflectance on an information recording surface by comparing brightness measured by the brightness detection circuit 6 in disk discriminating treatment with the threshold value stored in the storage means 9. The storage means 9 stores a coefficient, and the control means 8 makes the storage means 9 store a value obtained by multiplying the brightness detected by the brightness detection circuit by the coefficient stored in the storage means 9 as the threshold value in registration treatment of the threshold value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc discriminating apparatus for discriminating the type of a mounted disc.

[0002]

2. Description of the Related Art CD-RW (Rewritable) is music C
The reflectance is lower than that of D, CD-ROM, and CD-R (Write Once). Therefore, it has been considered to discriminate the disk based on the reflectance (see Japanese Patent Laid-Open No. 2000-311427).

[0003]

However, the measured value of the reflectance varies among the individual devices even for the same disc. A major cause of this is variations in the sensitivity of the light receiving element (four-division sensor), and other factors include variations in the tilt angle of the optical axis and variations in the reflectance of the disc. Therefore, if the threshold for determination is fixed, the determination result may be erroneous.

[0004]

The optical disc discriminating apparatus of the present invention has been made in view of the above point, and includes a luminous intensity detecting means for measuring the luminous intensity reflected on the information recording surface of the optical disc,
Discrimination of an optical disc having a different reflectance on the information recording surface by comparing the luminous intensity measured by the luminous intensity detection unit in the disc determination process with the threshold stored in the storage unit. An optical disc discriminating apparatus comprising a judging means, wherein the storing means stores a coefficient, and the judging means multiplies the luminous intensity detected by the luminous intensity detecting means in a threshold value registration process by the coefficient stored in the storing means. A value is stored in the storage means as the threshold value.

Further, the threshold value is set to an intermediate value between the maximum value of the reflected light intensity of the disk having the low reflectance and the minimum value of the reflected light intensity of the disk having the high reflectance, and the coefficient has a statistically small variation in the reflectance. It is set to a value that is added up by the reflected light intensity of the reference disc.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. The optical disc discriminating apparatus of the embodiment is a CD-RW
It is a device for discriminating between the CD and the CD-R.

FIG. 1 is a block diagram showing a main part of an embodiment of the present invention. (1) is a CD-RW or CD-R disc. A turntable (2) holds the disc (1) with a clamp (not shown). (3) is a motor for rotating the turntable (2).

Reference numeral (4) is a pickup, which is a laser diode (41) for emitting a laser, a polarized beam splitter (42) for transmitting a light component parallel to the incident surface and reflecting a light component perpendicular to the incident surface, A collimator lens (43) for collimating light, an eyepiece lens (44), a four-division sensor (45) for detecting the intensity of light in four areas, and an eyepiece lens on the surface of the disc (1) by the same principle as a speaker. Actuator for focusing (4
6).

The laser emitted from the laser diode (41) is reflected by the polarization beam splitter (42) in the direction of the disk (1), becomes parallel by the collimator lens (43), and is condensed by the objective lens (44). Emitted to the disc (1). The laser reflected by the disc (1) is irradiated onto the four-division sensor (45) through the objective lens (44) and the polarization beam splitter (42), and
The luminosity of one area is detected. In this way, the pickup (1) emits the laser focus toward the disc (1) and changes the luminous intensity of the laser reflected by the disc (1) to 4
It is divided into two areas for detection. Then, the focus of the laser can be moved in the focus direction.

Reference numeral (5) is a focus detection circuit, and FIG. 2 shows its detailed structure. The focus is determined from the difference in the luminous intensity detection signals of the four areas output from the four-division sensor (45) of the pickup (1). Detects whether or not they match. If the in-focus signal is +, the focus is in a distant position, if the in-focus signal is 0, the focus is in focus, and if the in-focus signal is −, the focus is in a close position.

Reference numeral (6) is a luminous intensity detection circuit, and FIG. 2 shows its detailed structure. The luminous intensity detection signals of the four areas outputted from the four-division sensor (45) of the pickup (1) are summed and amplified. . The luminous intensity of the laser reflection can be detected by this summed luminous intensity signal.

A focus servo circuit (7) drives a focus actuator (46).
Reference numeral (8) is a control circuit, which performs focus control, tracking control, and disc determination according to a program stored in the storage means (9). The storage means (9) comprises a non-volatile memory and a non-volatile memory. The non-volatile memory stores programs and initial information, and the non-volatile memory stores temporary information.

Next, the luminous intensity of the reflection of the disc (1) and the threshold value for disc (1) determination will be described. Disc (1)
Information is written at a position approximately 1.2 mm from the surface of the disk, and as shown in FIG. 3, when the laser focus is brought close to the surface of the disk (1) at a predetermined speed, the laser focus is changed to the disk (1). The first reflection occurs when the surface of the recording medium is reached, and the second reflection occurs when the information recording surface is reached.
As shown in FIG. 3, there is no difference in the reflectance of the surfaces of the CD-RW and the CD-R, and there is a difference in the reflectance of the information recording surface.

FIG. 4 is a diagram showing the difference in reflectance between CD-RW and CD-R. This value is the light intensity detection value measured by the inventor (total light amount of the four-division sensor (45) that receives reflection)
Is. The threshold value for determining the CD-RW and the CD-R is set to the center between the maximum value of the CD-RW having a low reflectance and the minimum value of the CD-R having a high reflectance. For this reason, a high reflectance type (CD-RW082H made by ABEX) was selected as the CD-RW. However,
Since this CD-RW with high reflectance has already been recorded, it has a large variation in reflected light intensity and is not suitable as a reference disc. Therefore, a blank CD-RW in which information was not yet written was measured as a reference disc. CD-
R has been selected as the one having a low reflectance, which has been written.

The measurement of the luminous intensity was carried out by four devices, and the minimum and maximum were obtained by measuring the light intensity a plurality of times with each device. CD
-The maximum value of RW (the larger of a2 and b2 in Fig. 4) and CD
The intermediate value (m) of the minimum values of −R is set as the threshold value of the device.
This threshold is a blank CD with small variations in reflected light intensity.
The value divided by the maximum value of −RW (a2 in FIG. 4) is the coefficient (FIG. 4).
K). In this embodiment, the average coefficient is 1.79.

Next, the registration of the threshold will be described. FIG. 5 is a diagram showing a threshold value registration operation of the control circuit (8). This registration process is a mode performed in the factory where the device is manufactured. The disc used as the reference disc is the blank CD-RW used in the calculation of the coefficient k described above,
There is little variation in reflectance. The control circuit (8) measures the luminous intensity (Vrw) of the reference disc (S1). This is multiplied by a coefficient k to obtain a second threshold value Vt2 (S2) and written in the storage means (9) which is a non-volatile memory (S3). And
Shipped from the factory.

Disc discrimination will be described below. FIG. 6 is a diagram showing the disc discriminating operation of the control circuit (8). When the disc (1) is set in the device, the control circuit (8) moves the objective lens (44) to a predetermined position (S11). This position is a position where the focal point becomes farther from the surface of the disc (1). From this position, the control circuit (8) brings the objective lens (44) closer to the disc (1) (S12).

Then, the control circuit (8) monitors whether or not the luminous intensity from the luminous intensity detection circuit (6) exceeds the first threshold value Vt1 (S13). As shown in FIG. 3, the first threshold V
t1 is a value set between the surface and the luminous intensity of the CD-RW. When the in-focus detection circuit (5) detects that the in-focus state is achieved without exceeding the first threshold value Vt1, it is determined that this position is the front surface (S14).

Further, the objective lens (44) is attached to the disc (1).
(S12), the control circuit (8) detects that the luminous intensity exceeds the first threshold value Vt1 (S13).
Y). Further, the objective lens (44) is brought closer to the disc (1) (S16), and it is monitored whether the luminous intensity exceeds the second threshold value Vt2 (S17). If it is detected that the in-focus state is achieved (Y in S18) while the luminous intensity does not exceed the second threshold value Vt2 (N in S17), the disc (1) is CD-
It is determined to be RW (S19).

If the luminous intensity exceeds the second threshold value Vt2 (S1
7), the control circuit (8) at that time the disc (1)
Is determined to be a CD-R (S20), and then it is detected that the focus is achieved (S21). As a result, in the case of the CD-R, the disc (1) can be judged before focusing, and the disc judgment time can be shortened.

In the above embodiment, CD-RW and CD-RW are used.
Although the judgment of R is made, the present invention is not limited to this, and the present invention can be applied to judgment of disks having different reflectances.

[0022]

As described above, according to the present invention, since the disc determination is performed by the threshold value calculated based on the luminous intensity of the reference disc actually measured for each device, the disc determination can be performed with high accuracy. .

Further, since the calculation is carried out on the basis of the disc having little variation, it is possible to perform disc determination with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of the present invention.

FIG. 2 is a diagram showing a detailed configuration of a focus detection circuit and a luminous intensity detection circuit.

FIG. 3 is a diagram showing a waveform of reflected light intensity of a disc.

FIG. 4 is a diagram showing a difference in reflectance between CD-RW and CD-R.

FIG. 5 is a flowchart showing a threshold registration operation.

FIG. 6 is a flowchart showing an operation of disc determination.

[Explanation of symbols]

1 disc 4 pickup 41 Laser diode 42 Polarizing beam splitter 43 Collimator lens 44 eyepiece 45 4-division sensor 46 actuator 5 Focus detection circuit 6 Luminous intensity detection circuit 8 control circuit 9 storage means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshishige Shimohi             3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori             Sanyo Electric Co., Ltd. (72) Inventor Hiroyuki Yumoto             3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori             Sanyo Electric Co., Ltd. (72) Inventor Katsushi Nishiyama             3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori             Sanyo Electric Co., Ltd. (72) Inventor Kazuhiko Ito             3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori             Sanyo Electric Co., Ltd. F term (reference) 5D090 AA01 BB03 BB04 CC09 CC18                       DD03 FF05 HH01 JJ11                 5D117 AA02 CC07 DD06 DD10 FF03

Claims (2)

[Claims] 1. A luminous intensity detecting means for measuring luminous intensity reflected by an information recording surface of an optical disc, a storing means for storing a threshold value of luminous intensity, a luminous intensity measured from the luminous intensity detecting means in a disc judging process and the storing means. An optical disc discriminating apparatus comprising: a discriminating unit for discriminating an optical disc having a different reflectance on an information recording surface by comparing with a threshold value stored in the storage unit; An optical disc discriminating apparatus, wherein a value obtained by multiplying the luminous intensity detected by the luminous intensity detecting means in the registration processing by a coefficient stored in the storing means is stored in the storing means as the threshold value. 2. The threshold value is set to an intermediate value between the maximum value of the reflected light intensity of a low reflectance disc and the minimum value of the reflected light intensity of a high reflectance disc, and the coefficient statistically has little variation in reflectance. The optical disc discriminating apparatus according to claim 1, wherein the optical disc discriminating device is set to a value obtained by adding the reflected light intensity of the reference disc.